Pilot lost rotor control at high speed

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A highly-regarded Queenstown pilot, killed in a helicopter crash, was flying fast when main rotor control was lost and the blades struck the tail boom, the Civil Aviation Authority says.

Wakatipu Aero Club operations manager and chief flying instructor Julian Kramer, 52, who was known as Julianne, died in the crash in the Cardrona Valley on November 8, 2012. The authority's investigation concluded Kramer was fit and a very experienced aeroplane pilot but had much less experience in a Robinson R22. Investigators were unable to establish the extent, if any, to which this inexperience contributed to the crash. Crash investigators found:

It was likely the pilot was under time pressure to complete the flight before a twilight cutoff.

A witness indicated the pilot was flying at high speed with a high rotor rate.

Main rotor control was lost, the main blades left the normal plane of rotation and struck the tail boom. After this, recovery was impossible.

The investigation could not establish why main rotor control was lost.

There were no technical/mechanical defects but the helicopter was 25 hours overdue for its 50-hour service.

A bird's nest on the engine was not a contributing factor.

The report said a witness heard the chopper "working hard" and another witness saw the R22 falling with the main blades stationary and without sound.

The report stressed it was not possible to ascertain whether Kramer's inexperience in flying helicopters contributed to the crash.

However, the report flagged a Robinson safety notice, which said "ingrained reactions for an experienced aeroplane pilot can be deadly when flying a helicopter".

The wreckage indicated significant damage at altitude before the chopper hit the ground and traces of paint on the main rotor, which was missing a 1-metre section, were matched to the tail boom.

Evidence from damage to the main rotor hub and masts revealed the blades flapped to extreme up and down angles, known as "main rotor divergence" when the rotor disk deviates from the normal level-flight plane.

R22 accidents due to main rotor divergence can be caused by low rotor RPM, turbulence, abrupt control movement or downward movements known as "low-gravity manoeuvres". Possible causes were considered, including a manoeuvre that caused the R22 to roll right that could take a pilot by surprise and lead to a rapid or incorrect response, manipulating the throttle in the wrong direction, or sudden turbulence. The pilot had logged fewer than 20 hours in an R22 and was "not overly proficient at the time", the report said.

Kramer, who had more than 30 years of experience in aeroplanes, was flying the helicopter, owned by Andrew Fairfax, back from Wanaka after the pair flew there earlier in the evening to collect a fixed-wing light aircraft. Both pilots left Wanaka Airport about 8.30pm to fly back to Queenstown via the Cardrona Valley but emergency services were informed the helicopter had crashed about 10 minutes later.